Railway traffic controlling apparatus



March 18, 19 1- .1. w. LIVINGSTON RAILWAY TRAFFIC CONTKOLLING APPARATUSFiled Sept. 7, 1939 w WE 0 5 .III .6. F W m Om m 1 5 M w 1--- 9 w m. a mTm My. a 2 5T 5 2 Z J V n a Z J 4 5- 5. 8 2 -J T. 4 6 WW 2 1 a 5 Z 2 40IF w l T 2 1 2 3 5 r f 5 2 4 P B w 8 2 ,4 I 2 1 Ha 3 6 0 5 J l w H16ATTORNEY Patented Mar. 18, 1941 umreo STATES RAILWAY TRAFFIC CONTROLLING APPARATUS John W. Livingston, Forest Hills, Pa., assignor toThe Union Switch & Signal Company, Swissvale, Pa., a corporation ofPennsylvania Application September 7, 1939, serial No. 293,783

7 Claims.

My invention relates to railway traffic controlling apparatus, and hasparticular reference to the organization of such apparatus into railwaytraffic controlling systems of the class in Which control of a railwaytrafiic controlling device is established by trailic conditions in aselected stretch of track independently of track circuits.

It has heretofore been proposed to govern traffic controlled relays bytrafiic conditions in a stretch of track independently of track circuitsthrough the medium of a light source and a light responsive devicearranged to co-operate therewith in such manner as to be responsive totrafiic conditions in the stretch. Such light responsive devicesgenerally control electronic tubes, which function as amplifiers for theassociated devices and control one or more relays of'the usual tractivearmature type. An object of my invention is the provision of novel andimproved means whereby the electronic tubes may be employed as relays insystems of the above type, thereby avoiding the use of relays of thetractive armature type.

Another object is to provide novel and improved means for selectivelycontrolling a control device in accordance with the control establishedby trafiic conditions upon relays of the electronic type.

A further object is the provision of means which provides a railwaytraffic controlling device with a detector track section having theshortest practicable dimensions.

An additional object is the provision of novel and improved means toenable a control lever to control a railway traffic controlling deviceto a position of correspondence under certain traffic conditionsadjacent the device, but to remove the lever from control of the deviceunder other traffic conditions.

Another object is to provide novel and improved means to at timesautomatically hold the control device in a position ofnon-correspondence with the control lever.

A further object is to provide novel and improved means in systems ofthe above type for displaying an indication when and only when theposition of the control device corresponds with the position of thelever.

Other objects and advantages of my invention will appear as thedescription proceeds.

I shall describe one form of apparatus embodying my invention, and shallthen point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing a preferred formof apparatus embodying my invention as applied to the control of arailway trafiic controlling switch.

Referring to the drawing, the reference character W designates atwo-position railway traflic controlling device associated with astretch of railway track X. Device W, as shown, may be a railway trackswitch movable between a normal position and a reverse position by meansof a suitable switch mechanism, designated by the reference characterSM. Mechanism SM is illustrated diagrammatically as direct acting switchmovement having a pneumatic motor, but it is contemplated that othertypes of motors, as for example an electric motor, may be employed ifdesired.

Switch mechanism SM has associated therewith a normal valve magnet NVand a reverse valve magnet RV, it being understood that When normalmagnet NV is energized, switch W is operated to its corresponding normalposition, and that when reverse magnet RV is energized, the switch thenis operated to its corresponding reverse position.

The reference character J designates a switch circuit controlleroperatively connected in the usual manner with switch W. Circuitcontroller J comprises six movable contact members I, 2, 3, 4, 5 and 6,each movable between a normal position and a reverse position. Contactmembersl to 5, inclusive, of controller J are con-- trolled by theposition of switch W in such manner as to be operated to their normalpositions (in which they-are illustrated in the drawing) at themid-stroke position of the switch when the switch is being operated toits normal position, and are operated to their reverse positions at themid-stroke position of the switch when the switch is being operated toits reverse position, In the normal positions of contact members l-5,the members engage fixed contact members I, B, 9, l and II,respectively, to form contacts 1-4, 2-8, 3-9, 4-40 and 5l i. In thereverse positions of members 1-5, fixed contact members l2, l3, I4, l5and I6, respectively, are engaged by contact fingers l-5 to formcontacts ll2, 2l3, 3-14, l l5 and 5-l6.

Movable contact member 6 of controller J is controlled by the positionof switch W in such manner that member 6 is operated to its normalposition to engage a fixed contact member I! and form contact 6ll whenand only when the switch occupies its full normal position, and member 6is operated to its reverse position 'to engage a fixed contact member l8to form con-- tact 6l8 when and only when the switch occupies its fullreverse position.

The reference character E designates a manually operable two-positioncontrol lever, which may, for example, be a switch control lever of aninterlocking machine. Lever E i operable be tween a normal position Nand a reverse position R, and is provided with contacts I9, 20, 2| and22, which are selectively closed in accordance with the position of thelever, the positions in which the contacts are closed being designatedin the drawing by the reference characters designating the position ofthe lever. For example, contacts I9 and 2| of lever Ei each bear thereference character N, indicating that contacts I9 and 2i are closedwhen and only when lever E is in its normal position N. Similarly,contacts 22 and 22 of lever E each bear the reference character R,indicating that contacts 20 and 22 are closed when and only when thelever is in its reverse position R.

Associated with lever E are two indication lamps KN and KR, the functionof which will be made clear presently.

Lever E and controller J cooperate to control suitable static relaymeans for controlling the operation of switch W. As herein shown, therelay means comprises two electronic tubes TI and T2, one tube Tl ofwhich is controlled under certain traffic conditions adjacent switch Wto be conducting and thereby enable switch lever E and switch circuitcontroller J to cooperate in controlling the operation of switchmechanism SM to cause the switch to be moved to its position ofcorrespondence with the lever. The other tube T2 is controlled to itsconducting condition by other traific conditions adjacent the switch toprevent switch mechanism SM from operating switch W to its position ofcorrespondence with the lever in the event that non-agreement existsbetween the switch and the lever under the latter traffic conditions.Tubes Ti and T2, as shown, are threeelement tubes each having two mainelectrodes, an anode or plate 23 and a cathode or filament 2'4, and acontrol grid 25 sealed within an envelope 26. Preferably, the envelope26 of each tube TI and T2 is filled with a suitable medium, such as neongas, which forms a conducting path between the two main electrodes whenand only when the potentialbetween these electrodes exceeds a valuewhich depends upon the relative potential of the grid with rspect to oneof the electrodes. Tubes Ti and T2 further are characterized by the factthat for a given plate potential, each tube is caused to operate andpass current only when its anode is positive with respect to itscathode.

The above-mentioned control of tubes TI and T2 by trafiic conditionsadjacent switch W is established by means of light-responsive devices,designated by the reference characters P with suitably distinguishingsufiixes, and their associated sources of light, which are designated bythe reference characters S with suitably distinguishing sufiixes. Asshown, two sources S (which preferably are constantly illuminatedelectric lamps) are located spaced apart along the stretch of track Xadjacent switch W, each source directing its beam of light across therails of the stretch to thereby define a detector track section for theswitch. Source Si preferably is positioned to project its beam over theheel of switch W. Located on the other side of the track in the path ofthe beam of source SI is a reflecting prism, designated by the referencecharacter H with a suitably distinguishing suffix, which splits into twoparts the beam of source SI, and projects one part of the beam or theother to one or the other of two light-responsive devices PI and P2associated with source SI.

Source S2 is located in advance of the points of switch W, and ispositioned to project its beam across stretch X so that, in the eventthat an operation of the switch has been initiated just prior to thebeam of source S2 being interrupted by a railway car moving toward theswitch, complete movement of the switch will be efiected prior to thecar arriving at the switch points. In the following description, it willbe assumed that the beam of source S2 is arranged to be projected acrosstrack X approximately ten feet in advance of the switch points, and thatthe distance between the two beams of sources SI and S2 is less than thelength of the shortest car to be operated over the switch. Located onthe other side of stretch X in the path of the beam of source S2 is aprism H2 which splits the beam of source S2 into two parts and projectsone part of the beam or the other to one or the other of twolightresponsive devices P3 and P4 associated with source S2.

The light-responsive devices P preferably are photo-electric cells ofthe type characterized by the fact that when illuminated or actuated bylight rays, the cells have relatively little resistance, but that whennon-illuminated or dark, the resistance of the cells increases andbecomes relatively large. As will be made clear presently,

photo-cells PI and P3 are included in series in a grid circuit for tubeTl in such manner that when a potential of a given magnitude is appliedacross the two electrodes of tube Tl, the tube is conditioned to beconducting when and only when cells PI and P3 are both actuated orilluminated. Photo-cells P2 and P4 are included in series in a gridcircuit for tube T2 in such manner that when a potential of a givenmagnitude is impressed across the two electrodes of tube T2, the tube isconditioned to be conducting when and only when at least one of thecells is unactuated or nonilluminated.

Having thus described the apparatus embodying my invention, I shall nowexplain its operation and at the same time shall trace in detail thecircuit connections of the system.

I shall first assume that the apparatus is in 4 its normal condition, asillustrated in the drawing, when switch W and lever E are both incorresponding normal positions and the stretch of track intermediate thetwo beams of sources S is unoccupied. In this condition of theapparatus, cells PI and P2 are actuated by the beam of source S! andcells P3 and P4 are actuated by the beam of source S2. Valve magnet NVof mechanism SM is energized over a normal circuit which may be tracedfrom one terminal of a suitable source of periodically varying current,such as a source of alternating current indicated as an alternator anddesignated in the drawing by the reference character G, through wire 28,wire 29, the winding of normal valve magnet NV, wire 30, normal contact4-40 of controller J, wire 3!, lever contact 2|, and wire 32 to theother terminal of alternator G. Indication lamp KN also is energized anddisplays an illuminated indication to signify that the switch W andlever E are in corresponding normal positions. An energizing circuit forlamp KN may be traced from one terminal of alternator G through wire 28,wire 33, normal contact ll-G of controller J, wire 34, the filament oflamp KN, wire 35, lever contact l9,

and wire 36 to the other terminal of alternator G.

With the apparatus in its normal condition above described, switch W maybe moved to its reverse position by operating lever E to its reverseposition. In this event, lever contact I9 is opened to open thepreviously traced circuit of indication lamp KN, which accordinglybecomes dark to indicate that switch W and lever E are out ofcorrespondence. Lever contact 2| also is opened upon movement of leverE, thereby opening the previously traced energizing circuit for normalvalve magnet NV, which accordingly becomes deenergized. However, withthe switch control lever in its reverse position, a circuit includingthe Winding of reverse valve magnet RV of mechanism SM is establishedthrough tube TI. This circuit passes from one terminal of alternator Gthrough wire 28, wire 31, the winding of reverse valve magnet RV, wire49, wire 38, normal contact 5-H of controller J, wire 39, filament 24 oftube TI, intervening tube space, plate 23 of tube Tl, wire 40, normalcontact 3-9 of controller J, wire 4|, wire 42, lever contact 22, andwire 32 to the other terminal of alternator G. The above circuitimpresses across the plate and filament of tube Tl an electromotiveforce having a magnitude selected to be below that efiective to breakdown the tube medium. However, cells PI and P3 are connected in seriesacross the filament 24 and grid 25 of tube Tl over a circuit which maybe traced from filament 24 of tube Tl through wire 39, wire 43,photocell Pl, wire 44, photo-cell P3 and wire 45 to grid 25 of tubeTl,and in addition, a grid resistor 48 and a condenser 41 are connectedacross plate 23 and grid 25 of tube Tl, as is readily apparent from aninspection of the drawing. The values of resistor 46 and condenser 41are so selected that, when alternator G impresses its electromotiveforce across plate 23 and filament 24 of tube TI, the tube is caused tobe conducting when and only when a low resistance path is establishedacross the grid and filament of the tube. Photo-cells PI and P3, whichare connected across the grid and filament by the circuit traced above,establish such low resistance path due to thefact that each of the twophotocellsis actuated by light rays from its associated source. Tube Tlaccordingly is caused to operate and pass current during each half cycleof alternatingcurrent that its, plate 23 is positive with respect to itsfilament, and consequently, reverse valve magnet RV is supplied withhalf-wave or rectified current during the period tube TI is controlledto its operating condition, The energization of magnet RV causesmechanism SM to operate switch W to its reverse position. Upon operationof the switch from its normal position, normal contact l|6 of controllerJ is opened, and when switch W reaches its mid-stroke position, normalcontacts I-'|, 2-8, 39, 4-lll and 5H of controller J are opened, andreverse contacts l-l2, 2-l3, 3-", 1-45 and 5I5 are closed. The openingof normal contacts 39 and 5H of controller J opens the previouslytracedcircuit of tube Tl, with the result that tube TI is restored toits normal non-operating condition. However, reverse valve magnet RV ismaintained energized over a circuit passing from one terminal ofalternator G through wire 28, wire 31, the winding of valve magnet RV,wire 49, wire 38, reverse contact 5-l6 of controller J, wire 42, levercontact 22 and wire 32 to the other terminal of alternator G, and switchW is operated 'to its full reverse position.

" When the switch reaches its full reverse position, a circuit then isestablished for indicator KR, which becomes energized to display itsilluminated indication signifying that the switch and control lever arein corresponding reverse positions. A circuit for energizing indicatorKR may be traced from one terminal of alternator G through wire 48,lever contact 20, the filament of lamp KR, wire 34, reverse contact 6-I8of controller J, wire 49, wire 38, reverse contact 5-[6 of controller J,wire 42, lever contact 22, and wire 32 to the other terminal ofalternator G.

To restore switch W to its normalposition, lever E is first operated toits normal position, thereby opening lever contacts and 22 to open thelast traced circuit for valve magnet RV and the previously tracedcircuit for indication lamp KR, which lamp then becomes dark to indicatethat lever E and switch W are out of correspondence. The closing oflever contact 2| establishes a circuit which includes valve magnet NVfor applying the electromotive force of alternator G across tube TI.This circuit extends from one terminal of alternator G through wire 28,wire 29, the winding of valve magnet NV, wire 30, reverse contact 4--l5of controller J, wire 39, filament 24 of tube TI, intervening tubespace, plate 23 of tube Tl, wire 40, reverse contact 3l4 of controllerJ, wire 50, wire 3|, lever contact 2!, and wire 32 to the other terminalof alternator G. Tube TI is conditioned to be operating in response tothe electromotive force applied by the above circuit by virtue of theaction of photo-cells PI and P3 (which are in their illuminatedcondition) establishing a low resistance path across the filament andgrid of tube TI, and consequently, valve magnet NV is supplied withhalf-wave current during the halfcycle periods that the plate of tube TIis positive with respect to the filament. The energization of magnet NVcontrols mechanism SM to cause switch W to move to its normal position.Upon the switch moving from its reverse position, reverse contact B-I8of controller J opens, and when the switch reaches its mid position,reverse contacts ll2, 2-l3, 3-l4, 4-15 and 5-46 are opened and normalcontacts l-l, 28, 3-9, 4--l0, and 5-H are closed. The opening of reversecontacts 3l4-and 4-|5 opens the circuit previously traced for tube Tl,with the result that tube Tl no longer operates. The normal circuithereinbefore traced for valve magnet NV, however, is now completed sothat operation of the switch is maintained until it reaches its fullnormal position. In the full normal position of the switch, normalcontact 6l1 of controller J closes to complete the previously tracedenergizing circuit for indicator KN, which becomes illuminated toindicate that switch W and lever E are in corresponding normalpositions.

From the foregoing, it is readily apparent that when the beams of bothsources SI and S2 are uninterrupted, the light-sensitive devices PI andP3 function to condition tube TI to be conducting when alternator Gimpresses its electromotive force across the tube electrodes. It isfurther apparent that, under the above conditions,

the electromotive force of alternator G is applied across the tubeelectrodes of tube Tl whenever lever E and switch W are out ofcorrespondence. It follows, therefore, that when lever E and switch Ware out of correspondence, control lever E and switch circuit controllerJ cooperate to connect across the electrodes of tube Tl in series withthe source of energy the particular one of the two valve magnets NV andRV that, when energized, controls switch mechanism SM to move the switchto its position of correspondence with lever E.

I shall now assume that during the interval that a railway car operatingin the stretch of track interrupts one or both of the beams of sourcesSI and S2, switch W and lever E are operated to a position out ofcorrespondence with each other. For example, I shall assume that withswitch W in its normal position and a car interrupting the beam ofsource S2, lever E then is moved to its reverse position. Under theabove condition, indication lamp KN becomes da-rlc due to the opening oflever contact I9 to indicate that the switch and switch control leverare out of agreement. Also, a circuit is established for connecting thenormal valve magnet NV across the two electrodes of tube T2 in circuitwith the source of energy. This circuit may be traced from one terminalof alternator G through wire 28, wire 29, the winding of normal valvemagnet NV, Wire 30, normal switch contact 4-43, wire 3|, wire 5|, normalcontact I-l of controller J, wire 52, the filament 24 of tube T2,intervening tube space, plate 23 of tube T2, wire 53, normal contact 28of controller J, wire M, wire 42, lever contact 22, and wire 32 to theother terminal of alternator G. Pho-tocells P2 and P4 are connected inseries across plate 23 and grid 25 of tube T2 over a circuit path whichmay be traced from grid 25 of tube T2 through wire 54, photocell P l,wire 55, photo-cell P2 and wire 56 to plate 23 of tube T2, .and inaddition, a grid resistor 51 and a condenser 58 are connected across thefilament 24 and grid 25 of tube T2. The values of resistor 51 andcondenser 58 are selected to condition the tube to be conducting inresponse to the electromotive force applied across its two electrodes byalternator G only in the event that a low resistance path is notestablished across the plate and grid of the tube. Such low resistancepath is provided by cells P2 and P5 when both cells are actuated, butwhenever one (or both) of the cells is unactuated, the low resistancepath is removed and tube T2 becomes conducting. Under the abovecondition, therefore, that is, with cell P4 unactuated due to a carinterrupting the beam of source S2, tube T2 is conditioned to beconducting since the high resistance of cell P4 causes tube T2 tooperate and pass current in response to the electnomotive force appliedacross its electrodes by alternator G, and tube T2 passes current duringthe intervals that its plate is positive with respect to its filament.Normal valve magnet NV interposed in circuit across the electrodes oftube T2 accordingly is energized by the half-wave or rectified currentpassed by the tube to maintain switch W in its normal position out ofcorrespondence with reverse position of lever E. The tube T2 remainsconducting during the interval that the car interrupts either or both ofthe beams of the sources SI and S2.

When the car vacates the detector track section as defined by the beamsof sources SI and S2, then the low resistance path is establishedthrough actuated cells P2 and P4 to establish a negative grid bias ongrid 25 of tube T2, and as a result tube T2 is controlled to itsnon-conducting condition. With photo-cells PI and P3 now actuated, tubeTI is controlled to its conducting condition by virtue of the positivegrid If, under the last assumed conditions (lever I E and switch W incorresponding reverse positions), the detector track section is enteredby a car in such manner as to trail the switch, the apparatus thenfunctions to hold the switch in its trailed position out ofcorrespondence with the lever. That is to say, if the beam of source SIis interrupted by the car entering the detector track section, tube T2is conditioned to be conducting and tube TI is conditioned to benon-conducting. Under the above condition, when switch W is moved pastits mid position in response to the trailing car, the circuit previouslytraced for tube T2 and including normal valve magnet NV is completed,whereupon normal valve magnet NV becomes energized to hold switch W inits trailed normal position out of correspondence with lever E duringthe interval that the car is on the detector track section defined bythe beams of sources SI and S2. When the detector section is vacated,however, tube T2 becomes non-conducting and tube TI becomes conductingto control switch W to its reverse position in correspondence with theposition of switch lever E, in substantially the same manner as waspointed out in detail hereinbefore in connection with the movement oflever E to a non-corresponding position when the detector section isoccupied.

In similar fashion, if lever E and switch W are in corresponding reversepositions and the detector section is occupied, a movement of the leverto its normal position out of correspondence with the position of switchW control-s tube T2 to cause mechanism SM to hold the switch in itsnon-corresponding reverse position. This is effected by virtue of thecircuit which extends from one terminal of alternator G through wire 28,wire 31, the winding of reverse valve magnet RV, wire 49, wire 38,reverse contact 5I6 of controller J, Wire 42, wire 59, reverse contactI-I2 of controller J, wire 52, the filament 24 of tube T2, interveningtube space, plate 23 of tube T2, wire 53, reverse contact 2-I3 ofcontroller J, wire 60, wire 3I, lever 2|, and wire 32 to the otherterminal of alternator G. When, however, 1

the detector section becomes vacated, then tube T2 is controlled to itsnon-conducting condition and tube TI is controlled to its conductingcondition, whereupon normal valve magnet NV becomes energized over itspreviously traced circuit including the two electrodes of tube TI, tocause mechanism SM to move switch W to its normal position in agreementwith the position of lever E.

In the event that switch W and lever E are in their respective normalpositions, and the switch is trailed by a car to interrupt first thebeam of source SI and then the beam of source S2, then thelast tracedcircuit for tube T2 is established whereby switch W is held in itsreverse position (to which it is moved by the trailing car) out ofcorrespondence with lever E until the detector section becomes vacated,in which latter event the switch is restored to its normal position inagreement with the position of lever E, as pointed out hereinbefore,

From the foregoing, it is readily apparent that when switch W and leverE are caused to be out detector section is occupied, the apparatusfunc-' tions to hold or look the'switch in its non-correspondingposition until such time as the section becomes vacated. This resultsfrom the fact that tube T2 is conditioned to be conducting when thedetector section is occupied and that lever E.and switch circuitcontroller J cooperate to connect across the electrodes of tube T2 inseries with the source of energy the particular one of the two valvemagnets NV and RV which when energized holds the switch in itsnon-corresponding position. When the section becomes vacated so thattube T2 is controlled to its non-conducting condition and tube Tl iscontrolled to be conducting, lever E and controller J then function toconnect across the electrodes of tube Tl in series with the source ofenergy the particular one of the two valve magnets NV and RV which whenenergized controls the switch mechanism to move the switch to itsposition of correspondence with the lever. It can be seen from theforegoing that tubes TI and T2 function as traflic controlled relays, inthat under certain traflic conditions in the detector section, the tubesare controlled to enable lever E to govern the operation of mechanism SMin such manner that switch W is always controlled to a position ofcorrespondence with lever E, but that under other tramc conditions inthe detector section, the tubes then are controlled so that if theswitch and control lever are out of correspondence, switch mechanism SMis controlled to cause the switch to be held in its noncorrespondingposition.

It should be pointed out that tralfic controlled relays controlledindependently of track circuits are-particularly advantageous for use incontrolling the operation of a trafiic controlling switch in freightclassification yards. This results from the fact that when relays arecontrolled by means other than track circuits, the detector tracksection can be shortened to a distance only a little greater than theshortest car operated over the switch, whereas when track circuitcontrol is employed, the track circuit is of necessity at least as longas the distance between the trucks of the longest car operated over theswitch. It can be seen, therefore, that since switching yard apparatusis operated most efficiently and economically when the headway betweensuccessive cars is the shortest possible, use of photo-cell controlledrelays enables the shortest practicable detector section to be employed,thereby enabling the switching apparatus to operate at its highestefliciency.

It should further be pointed out that use of the usual tractive armaturetype relays is avoided by apparatus embodying my invention, since theamplifying tubes generally used in connection with photo-cells toestablish control of relays are replaced by grid-glow tubes controlledby the photo-cells to function as circuit breakers. It follows,therefore, that apparatus embodying my invention provides novel andimproved systems requiring a minimum of apparatus which 1) providescontrol of the switch movement to operate the switch to its position ofcorrespondence with the switch lever when the detector section isunoccupied, (2) prevents operation of the switch in response to a levermovement when the section is occupied, (3) automatically holds theswitch to its trailed position during the intervals the section isoccupied, regardless of the position of the switch control lever, and(4) restores a trailed switch to its position of correspondence with thecontrol lever when the section becomes unoccupied.

Although I have herein shown and described only one form of railwaytraflic controlling apparatus embodying my invention, it is understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim; is:

1. In combination with a stretch of railway track provided with atwo-position railway traffic controlling device operatively connectedwith an operating mechanism for selective operation to each of its twopositions, said device having a circuit controller provided withcontacts selectively controlled in accordance with the position of saiddevice, a manually operable two-position control lever, means forprojecting beams of light across said stretch of track for defining atrack section adjacent said device, two electronic tubes, meansresponsive to said beams of light for controlling one of said tubes tobe conducting when and only when at least one of said beams of light isintercepted and for controlling the other of said tubes to be conductingwhen and only when none of said beams is intercepted, and circuit meanscontrolled by said control lever and by said circuit controller andincluding said two electronic tubes for controlling said operatingmechanism in such manner that when none of said beams is interceptedsaid control device is operated to a position of correspondence withsaid lever upon movement of the lever and when at least one of saidbeams is intercepted said control device is held in a position out ofcorrespondence with said lever upon movement of the lever. V

2. In combination, a stretch of railway track, a detector track sectionfor said stretch defined at each end by a source of light and alightresponsive device cooperating therewith in such manner asto beresponsive to trafiic in said stretch, a two-position trafiiccontrolling device positioned adjacent said section, a circuitcontroller operatively connected with said device, operating means forselectively operating said control device to each of its two positions,two electronic tubes, means controlled by said light-responsive devicesfor conditioning one of said tubes to be conducting when and only whensaid section is unoccupied and for conditioning the other of said tubesto be conducting when and only when said section is occupied, atwoposition manually operable control lever, and control means governedby said control lever and said circuit controller as well as by theparticular one of said two tubes conditioned to be conducting forcontrolling said operating means in such manner that said trafficcontrolling device is operated to a position of correspondence with saidlever when said section is unoccupied and is held in its last-operatedposition regardless of the position of said control lever when saidsection is occupied.

3. In combination, a stretch of railway track provided with a railwaytrack switch, a switch mechanism operatively connected with said switchand having a normal magnet and a reverse magnet for operating saidswitch to its corresponding normal position and reverse position, aswitch control lever having a normal position and a reverse position,two electronic tubes, means responsive to trafiic conditions in a givenzone of said stretch adjacent said switch for conditioning one of saidtubes to be conducting when and only when said zone is unoccupied andfor conditioning the other of said tubes to be conducting when and onlywhen said zone is occupied, means controlled by the position ofsaidswitch for connecting the non-corresponding magnet of said mechanism incircuit with said one tube and for connecting the corresponding magnetof said mechanism in circuit with said other tube, and means efiectivewhen said switch and said lever are out of agreement as to position forconnecting a source of current to said tubes for controlling to itsoperating condition that tube conditioned by traffic conditions in saidzone to be conducting, whereby non-agreement of the switch and switchlever when said zone is unoccupied causes said switch movement tooperate the switch to its position of agreement with said switch leverbut non-agreement of the switch and switch lever when said zone isoccupied causes said switch movement to hold said switch at its positionout of agreement with said lever.

4. In combination with a section of railway track provided with arailway track switch operatively connected with an operating mechanismfor selective operation to each of its two positions, a circuitcontroller operatively connected with said switch, a manually operabletwoposition switch control lever, two electronic tubes, means responsiveto trafiic conditions in said section for conditioning one or the otherof said two tubes to be conducting according as said section is or isnot occupied, and circuit means controlled by said control lever andsaid circuit controller and including said two tubes for controlling theoperation of said operating mechanism, whereby when said other tube isconducting said switch is operated to a position of correspondence withsaid lever but when said one tube is conducting said switch is held inits lastoperated position regardless of the position of said controllever.

5. The combination with a railway track switch located in a stretch ofrailway track and operated by a switch mechanism] to a position ofcorrespondence with a manually operable switch lever having a normalposition and a reverse position, said switch having a circuit controllerprovided with contacts selectively controlled in accordance with theposition of said switch, of two electronic tubes, means responsive totrailic conditions in a given zone of said stretch adjacent said switchfor conditioning one or the other of said two tubes to be conductingaccording as said given zone of track is or is not occupied, a source ofenergy, means controlled by said lever and said circuit controller andefiective when said lever is out of correspondence with said switch forconnecting said source across said two tubes, and means operated by thecurrent passed by the particular tube controlled by the traificconditions in said given zone of track to be conducting for controllingthe operation of said switch mechanism in such manner that if said onetube is conducting said switch is held in its position out ofcorrespondence with the lever but if said other tube is conducting saidswitch is moved to its position of correspondence with the lever.

6. The combination with a stretch of railway track provided with arailway track switch operated by a switch mechanism to a position ofcorespondence with a manually operable switch lever having a normalposition and a reverse position, said switch having a circuit controllerprovided with contacts selectively controlled in accordance with theposition of said switch, of a track section for said stretch defined ateach end by a source of light and a light-responsive device cooperatingtherewith in such manner as to be responsive to traflio in said stretch,two electronic tubes, means controlled by said lightresponsive devicesfor conditioning one or the other of said tubes to be conductingaccording as said section is or is not occupied, a source of energy,means controlled by said lever and said circuit controller and efiectivewhen said lever is out of correspondence with said switch for connectingsaid source across said two tubes, and means operated by the currentpassed by the particular tube controlled by the traiiic conditionsadjacent the switch to be conducting for controlling the operation ofsaid switch mechanism in such manner that if said one tube is conductingsaid switch is held in its position out of correspondence with the leverbut if said other tube is conducting said switch is moved to itsposition of correspondence with the lever.

7. The combination with a switch control lever having normal and reversepositions and a railway track switch located in a stretch of track andhaving corresponding normal and reverse positions, said switch having acircuit controller provided with contacts selectively closed inaccordance with the position of said switch, of two electronic tubes,means controlled by traffic conditions in a zone of said stretchadjacent said switch for controlling one or the other of said two tubesto be conducting according as said zone is or is not occupied, a sourceof energy, circuit means controlled by said lever and by said circuitcontroller and efiective when and only when said lever and said switchare out of correspondence for connecting said source across said twotubes, switch operating means for reversibly operating said switch, andmeans controlled by the current passed by the particular tube selectedby trafiic conditions in said zone to be conducting for operating saidswitch op erating means in such manner that if said one tube isconducting said switch is held in its position out of correspondencewith said lever but if said other tube is conducting said switch ismoved to its position of correspondence with said lever.

JOHN W. LIVINGSTON.

